1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, an improvement in performance of thin film magnetic heads has been sought in accordance with an increase in the areal recording density of hard disk drives. As magnetic recording systems applicable for the hard disk drives, for example, a longitudinal recording system that a signal magnetic field is oriented in an in-plane direction of a recording medium (a longitudinal direction) and a perpendicular recording system that the signal magnetic field is oriented in a direction perpendicular to the recording medium are well-known. At present, the longitudinal recording system is widely used, but the perpendicular recording system instead of the longitudinal recording system holds promise for future, because the perpendicular recording system can obtain an advantage that, for example, a recording medium in which data has been already recorded has resistance to thermal decay effects, and higher liner recording density can be achieved.
As recording modes using the perpendicular recording system, for example, a mode of recording in a single-layer recording medium by the use of a ring head comprising two magnetic layers facing each other with a gap in between on a side of an end and magnetically coupled to each other on a side of the other end, a mode of recording in a two-layer recording medium by the use of a single-layer head (single pole type head) and so on have been proposed. Among them, in the mode using a single-layer head and a two-layer recording medium, resistance to thermal decay is extremely superior, so it becomes a focus of attention as a mode which can improve the performance of the thin film magnetic heads.
In order to improve recording performance of a single-layer thin film magnetic head using the perpendicular recording system, it is required to emit necessary and sufficient magnetic fluxes from a head (main magnetic pole) to increase as high strength of the perpendicular magnetic field as possible. Techniques for increasing the strength of the perpendicular magnetic field include, for example, a technique of comprising the main magnetic pole with a cross sectional area parallel to a recording-medium-facing surface (air bearing surface) facing the recording medium which is reduced with increasing proximity to the air bearing surface. A specific example of the technique is described in, for example, a specification (Japanese Patent Application No. 2000-343245) applied by Sato et al. The main magnetic pole described in the specification has a structure that the width of the main magnetic pole is reduced with increasing proximity to the air bearing surface. As for the main magnetic pole, according to reduction in the cross sectional area, magnetic fluxes passing through the main magnetic pole are gradually concentrated, so the magnetic fluxes reach an edge of the main magnetic pole.
Moreover, in Page 67 of Nikkei Electronics No. 789 (Feb. 12, 2001), a structure that a bottom portion of a magnetic pole is partially removed is introduced.
However, in spite of various considerations of the structure of the main magnetic pole in conventional thin film magnetic heads using the perpendicular recording system, the strength of the perpendicular magnetic field is still not sufficient enough in view of future movement in areal recording density which is expected to be further increased. In order to prove the practicability and future potential of the perpendicular recording system to expand the use of high-capacity hard disk drives using the perpendicular recording system, securing as high strength of the perpendicular magnetic field as possible is an urgent matter.
Incidentally, the structure of the magnetic pole introduced in the above Nikkei Electronics is considered to be useful for securing the strength of the perpendicular magnetic field. However, a specific manufacturing method which is important to implement the structure of the magnetic pole is not described, so it is uncertain about whether the structure of the magnetic pole can be actually manufactured and whether it is useful.